Technical Field
Embodiments described herein are related to the field of high-speed interface design, and more particularly to reducing noise resulting from simultaneous switching.
Description of the Related Art
Computing systems typically include a number of interconnected integrated circuits. In some cases, the integrated circuits may communicate through parallel interfaces, which simultaneously communicate multiple bits of data. In other cases, the integrated circuits may employ a serial interface, which sequentially communicates one bit of data at a time. In some cases, both parallel and serial interfaces, individual bits of communicated data may be differentially encoded.
In a computing system, the integrated circuits may have different power supply requirements, which may result in different output voltages being coupled to the integrated circuits' respective communication ports. Furthermore, variations in the properties of wiring traces on circuit boards as well as differences in power supply performance, may further contribute to differences in the power supply voltages supplied to the integrated circuits. Switching of output circuits during the transmission of data from one integrated circuit to another may further contribute to variations in the voltage levels of the power supplies.
Data transmitted between integrated circuit may be encoded to aid in transmission. For serial interfaces, data may be encoded to provide sufficient transitions between logic states to allow for clock and data recovery circuits to operate properly. Data may be encoded to include an even or nearly even number of logical zeros and ones, prior to transmission across parallel interfaces to reduce noise or improve signal integrity.